I have a treated room and am using 145" 2:35 1.3 gain screen. I will likely keep this projector for several years. The big question is the upgrade to either of the more expensive projectors worth it assuming all are in my budget range?

I have to decide during preorder period or they WILL NOT be in my budget range.

This is a funny question....
For the reason that i was (am) in the same position as you. I have wondered if the 48 is good enough. Especially at the AVS price! I have spent more in the past and got a much inferior product.
My thinking is that the the 48 is a better deal than the 56. However if your budget can be easily stretched to the 66 then go for that. The additional contrast you gain might be worth it. Unfortunately I can't stretch my budget to the 66. On the other hand, your screen is much bigger than mine and the 66 is a bit dimmer than the 48, so not sure if the screen size and the lumens will give you the brightness you need. (that is also very personal how much brightness you like.) I would be OK at my size (96 diagonal) for brightness and I like a bright image for football and such with some company over and a bit of light on in the background.
Alas my theater is still being built so I have not joined the pre-order. I probably need 6 more months....
Anyways, i think you have a great projector on order and you will be happy with it unless you need that bit of extra contrast the 66 might give you for considerably more money.
Zed

Thanks for the reply Zed. At this point I may stick where I am. I doubt the 66 is worth the premium to me as I am not sure how sensitive I am about subtle picture improvements. Maybe someone else will tell me to definitely go for it?

I was in the same boat you were In, the 4810 or the 56. After weeks of going back and fourth I decided on the 4810 for 2D and since 3D is important to me the BenQ W7000 for 3D. If you are interested in 3D and have no problem with rainbows, this is the perfect set up in my opinion.

Why don't you call Mike G. and let him explain whether you need the extra contrast for your particular set up. The difference in lumens is insignificant and will look less than 3% different in intensity to your eyes. The on off is critical if you want to rung the big boy gammas of 2.4. Toy need about 40,000 to one one on off to run such a gamma without the dreaded strike you dead in your chair BLACK CRUSH.Remeber a units rated on off is at long throw, minimum iris, low lamp and if you are human that willl probably not be your set up and operating mode. You very likely will need the extra on off of the 56 so that with your set up and operating conditions you will get an effective on off of 40,000. Of course you can just run a lower gamma, like 2.2 and then you simply do need the extra on off and you would barely notice the difference. Talk to Mike. I am gone for today on the road.

Why don't you call Mike G. and let him explain whether you need the extra contrast for your particular set up. The difference in lumens is insignificant and will look less than 3% different in intensity to your eyes. The on off is critical if you want to rung the big boy gammas of 2.4. Toy need about 40,000 to one one on off to run such a gamma without the dreaded strike you dead in your chair BLACK CRUSH.Remeber a units rated on off is at long throw, minimum iris, low lamp and if you are human that willl probably not be your set up and operating mode. You very likely will need the extra on off of the 56 so that with your set up and operating conditions you will get an effective on off of 40,000. Of course you can just run a lower gamma, like 2.2 and then you simply do need the extra on off and you would barely notice the difference. Talk to Mike. I am gone for today on the road.

mostly i watch sports and use a 2.2 gamma. When I receive a movie over the set top box i generallt just leave the gamma at 2.2. When I bother to watch a Bluray from my cheap[ Bluray player, I do use a 2.4 gamma and of course switch to a film mode yada yada.

gammas are a preference and I really don't think they make that much difference to enjoyment. One prefers one over the other but its still like all good sex.